Cryogenic storage vessel

ABSTRACT

A ship for the transportation and storage of cryogenic temperature fluid wherein an inner insulation composite protects the container and ship hold from detrimental effect of such temperature. Resin impregnated fabric and perforated foil comprise a porous liner bonded to fiber-reinforced foam layers to form gaseous boundary layer insulation.

United States Patent 1191 Lemons 1 June 4, 1974 1 CRYOGENIC STORAGE VESSEL 3,400,849 9/1968 Pottier et al 220/9 1.0 3,671,315 6/1972 [a s." 220/9 LG X [75] Inventor: R01) Lemons westmmster 3,489,311 1/1970 Fo lle l 'ts et Z11. 220 9 R Cahf- 3,640,920 2/1972 Cear 260/25 AK A g e McDonnell D g C p 3,675,809 McGrew 2211/9 LG Santa Monica, Calif. Przmary Exammer-George E. Lowrance 1 1 Flledi P 3, 1972 Assistant Examiner-Steven M. Pollard [2] 1 App]. No; 240,362 Attorney, Agent, or FirmRobert 0. Richardson; Walter .1. Jason; Donald L. Royer [52] US. Cl 220/9 LG, 220/9 R [51] Int. Cl B65d 25/18 [57] ABSTRACT [58] Pick] of Search H 220/9 R 9 LG, 88, 9 F; A ship for the transportation and storage of cryogenlc 1 14/74 A temperature fluid wherein an inner insulation composite protects the container and ship hold from detri- [56] References Cited mental effect of such temperature. Resin impregnated fabric and perforated foil comprise a porous liner UNITED STATES PATENTS bonded to fiber-reinforced foam layers to form gase- 2,676,773 4/1954 Sanz ct a1. 220/9 LG ous boundary layer insulation. 3,009,601 11/1961 Matsch 220/9 LG 3,243,931 4/1966 Becherer 220/9 R X 10 Claims, 7 Drawing Figures 3,267,685 8/1966 Schroeder 220/9 LG 1 CRYOGENIC STORAGE VESSEL BACKGROUND. OF THE PRESENT INVENTION In. various parts of the world there is a serious shortage of methane (LNG) or natural gas which is approximately 90 percent of the output from gas wells. Pipe lines are routed over land from the used gas wells to high density population areas where its use is in great demand. As these gas wells become exhaustedor where demand exceeds supply, additional sources must be obtained. In some cases a butane or propane (LPG) gas familiarly known to campers as bottled gas may be used. However, this accounts for only about percent of the gas supply from the gas wells. The problem is thus presented as to how to obtain supplies of natural gas from overseas sources. Since 1 gallon of methane gas in liquid form is approximately equivalent to 638 gallons in gaseousform, it obviously is highly desirable to transport the gas in its liquid form. To this end, containers, cargovessels and ships-are being designed for the storage and transportationof methane or natural gas in its liquid form;

The shipment of natural gas in liquid form in ocean going vessels presents a serious safety problem because economies dictates that ships be made using a shipbuilding quality carbon steel. This type of mild steel becomes brittle at sub-zero temperatures and will readily crack open if subjected to 258F., the temperature at.

which methane, LNG, becomes a liquid, creating a catastrophic rupture of the ship's hull. Since peoples lives are at stake at sea, there is an overpowering requirement for a reliable insulation between the liquid methane and the steel tank structure. One solution to the problem now in practice is to use welded corrugated relatively thin stainless steel liners having bolsa wood insulation on plywood sheets. However, this method was very costly since it involved miles of welded joints in thin steel that would not stay flat and the welds were continually leaking, requiringconstant inspection and repairs after each voyage. Another method was to use a welded lnvar (low contraction steel alloy) which also suffered from service weld cracking and required constant repairing. Within this liner were plywood boxes filled with powered Perlite, a silicate fluff of volcanic ash, which served as insulation. This ash also absorbed water which destroyed its effectiveness. Another solution was to apply loose bag liners which would rip open when fluid sloshing occurred. Another method used in the shipment of liquid butane at 40F. was to use a neat, unreinforced. foam with a glass laminate liner. However, this does not work at cryogenic temperatures such as at 258F. in the case of methane because of this temperature the foam-liner joint ruptures. All of these methods placed emphasis upon using liquid-tight, impermeable liners. Leak detection devices were used to prevent possible fire or explosion due to leakage of liquid gas into the warm interior of the insulation where the rapid expansion of gases would blow large segments of insulation from the container wall.

SUMMARY OF THE PRESENT INVENTION An ocean going vessel has been developed with a multiple of liquid fluid storage compartments, each having inner liners which are porous and have a permeability that may be achieved with'a single ply of glass fabric impregnated with a polyurethane or epoxy resin,

' range of values. The porosity of the liner allows the pressure within the reinforced foam insulation to reach a state of equilibrium or near equilibrium with the liquid inside the vessel compartments as they are being filled, emptied or stored; The cryogenic liquid is thus contained within a gaseous envelope within the insulative foam composite within the container or vessel compartment. The gas-liquid interface occurs very near the liner and most often appears somewhat inside the insulation. The insulation consists of a plurality of pre-fabricated 3D foam blocks or segments bonded together to form long and narrow segments with interlocking edges to provide for maximum flexibility in mating with the contours of the marine vessel, and to permit a significant area of liner-insulation composite to be applied with a minimum of time of installation inside the vessel. A perforated electrically conducting film or strip may be bonded to the liner outer surface (the surface exposed to the liquid) to serve as a static electrical discharge element and to serve as a barrier against flame propagation. In the case of roof insulation, these strips are mechanically held in position until a vacuum bag could be installed thereover/These strips are vacuum bonded to the walls of the vessel.

Damage to the insulation is readily detectable by visual examination and easily repaired with a splice. Debonding can be detected before reaching a serious stage by observing frost patterns on the vessel. Thus, the insulation materialmay be accomplished at low cost and is highly reliable in use. These internally insulated tanks may be used for transporting or storage of liquified gas at cryogenic temperatures as low as 423F. (liquid hydrogen) and can be used for transporting or storage of fluids under high pressure or at atmospheric pressure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view illustrating the insulation system installed within a ships hull;

FIG. 2 is a perspective view showing the construction detail of one prefabricated segment or LOG" of insulation to be bonded to the tank wall;

.' FIG. 3 is an elevational view taken along line 3-3 in FIG. 1;

FIGS. 4, 5 and 6 are sectional views showing corner joints; and

FIG. 7 is an elevational view showing hooks on ceiling or overhead tank wall insulation attachments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS FIG. 1 shows a marine vessel 10 for the transportation of liquified natural gas such as liquid methane and including thermally insulated cargo tanks 12 integrally supported inside the cargo holds and having the general configuration of the cargo holds. In this case, the ship 10 is provided with an outer hull l4 and an inner hull l6 spaced from outer hull 14 by spacers 18. The space 20 between the inner and outer hull may be used for storage or water ballast asdesired. The inner hull I6 is integrally lined with heat insulation material comprising an inner insulation layer 22 covered with a porous liner 24; A second or outer insulation layer 26 with porous liner 28 is bonded to the first and a perforated conductive foil 30 completes'the insulative composite. Retention fasteners 32 in the ceiling are used to retain the composite until the vacuum bonding has been accomplished upon installation. Other retention fasteners 33 such as glass fiber or other non-metallic cord may be anchored to the walls 35 and floor 37 of the container hull 16. These fasteners extend through the insulation and liners to serve as high load attach points to support slosh baffles and other internal structures not shown.

The insulation layers 22, 26 and liners 24, 28 are shown in FIG. 2 as elongated strips or logs 34, 36. Typically, these logs will be about 90 feet long, about 2 feet wide and 6 inches thick. Each log consists of a plurality of blocks of three-dimensional reinforced foam covered with a fiber glass cloth liner in a manner to be more fully explained hereinafter. A strip of perforated aluminum foil 30 with pin holes approximately one-half inch on center is applied to the inner liner to reduce fire hazard, particularly when the logs are installed. These prefabricated segments, long and narrow, provide maximum flexibility to mate with the contours of a'marine vessel and allows a significant area of liner-insulation compositeto be applied with a minimum of time inside the vessel for installation.

Referring now to the enlarged fragmentary view in FIG. 3, each of the layers 22, 26 are made from a plurality of blocks 38' which consist of foam 40 having X, Y and Z reinforcing fibers 42, 44 and 46. These blocks may be of the type, and made by the method, set forth in U.S. Pat. No. 3,322,868 for Three-Dimensional Reinforced Structure by Kruse and Rossello which issued May 30, [967, the subject matter of which is hereby incorporated by reference. Of course, other materials and methods of fabrication may also be used as desired provided they serve the purpose intended.

A fiber glass liner 24 is bonded to the outer ends of the Z fibers 46. and the abutting ends of the blocks 38 are also bonded together to form the elongated strips or logs. These are then bonded to the inner surface of the inner hull 16 of the vessel. The edges of the liner 24 are then taped with splices 48. The second layer 26 with fiberglass liner 28 is vthen bonded to the first liner' 24, and splices 50"applied. A polyurethane or epoxy resin may be used to impregnate and bond (while wet) the liner to the fiber ends. The amount of resin used preferably is about 1.5 times the weight of the dry glass fabric. This usually is referred to as a 60 percent by weight resin content laminate. It has been found that resin in the amount of 2 /2 times the weight of the fabric causes cracking due to contraction at a -423F. temperature and,-in the amount of only one, the bond strength to the foam is marginal and a high reliability bond is not achieved.

In FIGS. 4, and 6 there are shown several comer connections. In FIG. 4, four columns or posts 52, 54, 56 and 58 of foam wrapped in a fiber glass lining are placed in a corner at the intersection of container walls 60, 62. Fiber glass splices 64 are applied to the inner corners of the inner and outer layers 66, 68 of insulation having liners 70, 72 on their inner faces. A comer splice 74 then completes the porous seal. In FIG. 5 the corner formed by container walls 76, 78 has the end 80 of inner layer 82 abutting wall 78, with end 84 of inner layer 86 abutting end 80. The fiber glass liner 88 is then wrapped around the corner over the inner ends of Z fibers 90 of both layers. Thereafter outer layer 92 is ap- 4 plied with its end 94 abutting end 84 of layer 86, and end 96 of layer 98 is then placed against end 94. Fiber glass liner 100 and a perforated aluminum foil 102 is then applied. In FIG. 6 the inner layers 104 and 106 have tapered abutting ends 108, 110 meeting at the corner of container walls 112, 114. Their respective fiber glass liners 116, 118 wrap around their ends and contact the container walls 112, 114. Similarly, the outer layers 120, 122 have tapered abutting ends 124, 126 with fiber glass liners 128, I30 extending around the ends for bonding to liners 116 and 118 respectively.

- In FIG. 7 there is shown a technique for attaching the insulation to the top of the container. In the upper corner 132 is a scaffold support hook 134. The side insulation 136 is applied to side wall 138, leaving hook 134,

exposed for attachment of scaffolding. Insulation fastening devices 140 are attached to the underside of roof or top 142. Preferably, they may be shafts with barbs on the end since they are needed only to hold the adhesive-coated insulation strips 144 in position against the ceiling until a vacuum bag can be installed for the bonding process. For illustrative purposes sections 146 and 148 of the insulation are shown as yet to be pushed onto fasteners 150. When installed, the hooks lock under the X and Y fibers within the foam. After the ceiling insulation has been applied, the scaffolding is removed and insulation wedge 154 is applied to the corner 132.

INSTALLATION PROCEDURE For purposes of explaining the procedure for installing the insulation in a ships hold, it is assumed that the insulation blocks have already been converted into elongated strips for maximum flexibility and minimum installation time. One form of block construction is described in the Kruse and Rossello patent previously referred to and another form is set forth in my copending application Ser. No. 240,524 filed Apr. 3, 1972 for Fabrication of Three-Dimensional Reinforced Insulation Blocks. With a supply of elongated strips or logs on hand, the vessel wall is then cleaned and prepared for bonding. The strips are coated with an adhesive and positioned against the wall. Aftera series of strips covering about 1,000 square feet of area have been placed, a vacuum bag isthen used to apply'pressure (about 20 inches of mercury or 10 p.s.i.) during the cure cycle of the adhesive. The adhesive resin bonds at ambient temperature (77F.) for 24 hours or at F. for 3 hours. This sequence is repeated to bond all strips of insulation to the vessel. After the vacuum bag cure cycle is complete, the liner splices are then applied but no external pressure is needed in liner-to-liner bonding. This process allows the critical bonds of liner-to-reinforced foam to be made outside the cryogenic container and under best environmental conditions, using preferred quality control measures. Only the bond to the vessel and the less critical liner splices need be accomplished inside the vessel.

As the insulated vessel is filled with cryogenic fluid, a small'amount of fluid will permeate slowly through the porous liner where the warmer temperature promptly turns liquid to gas thus creating a reverse or offsetting pressure to prevent further liquid penetration. This conversion of cryogenic liquid to gas taking place at, or just under,the liner surface occurs within the cell size of the foam or in such minute volume that the porosity within the liner provides ample escape paths which prevent the reverse gas pressure from exceeding the liner bond rupture strength.

Within a short period of time after filling the insulated vessel with cryogenic fluid the temperature gradient across the insulation thickness reaches a measure of stability and the gas pressure within the foam insulation will approach near equilibrium with the fluid pressure at the liner surface. The foam insulation will eventually become permeated with the gas type being carried in liquid form, such as hydrogen gas when LH (liquid hydrogen) is being carried, or methane when LNG (liquid natural gas) is being carried. The thermal conductivity of the insulation, therefore, will be slightly less than that of the gas type being carried and thus the container is insulated from the liquid gas. The reinforcing fibers within the foam are firmly bonded to the vessel wall and are also firmly bonded to the liner. Both of these bonds must be sufficiently strong to withstand the momentary pressure differential fluctuations during filling the vessel with cryogenic fluid and when emptying the vessel. In addition, these bonds must withstand the loads transmitted to the insulation composite by racking and bending of the vessel in rough seas, along with the forces generated by the cryogenic fluid creating sloshing waves against the surface of the liner.

More than ample strength is available in this insulation composite to accommodate these functional requirements provided the installation process is not compromised by adopting designs and bonding techniques solely related to the shear size of the vessel being insulated. For this reason this invention constitutes a novel but realistic approach toward achieving the degree of reliability vital to the successful performance and required service life span of the vessel.

Damage to the insulation in the form of liner cracks is readily detected by visual examination of the liner surface and easily repaired with a splice. Debonds between liner and fiber-reinforced foam are also readily detected using proven methods with sonic brush examination, and are repaired by replacing the damaged area. The high tolerance of the insulation system to sustain damage or personnel abuse and still function reliably as cryogenic insulation is noteworthy and small areas of surface damage need only be repaired to maintain the insulation required to achieve minimum boiloff rates of the liquified gas cargo.

Even a debond condition against the vessel wall can be detected before reaching the serious stage by ultrasonic inspection or by observing frost patterns on the outside of the vessel wall and can be repaired by using the same techniques as used to install instruments through the insulation after bonding is completed. As yet, no insulation debonding has occurred in cryogenic service of operational vessels where the bonding practices forming the principles embodied by the approach just described have been followed.

Having thus described an illustrative embodiment of the present invention, it is to be understood that modifications thereof will become apparent to those skilled in the art and it is to be understood that these deviations are to be construed as part of the present invention.

I claim:

1. A vessel for receiving liquified gas at cryogenic temperatures as low as 423F., said vessel having a supporting wall to which is bonded oriented fiberreinforced plastic foam to which a permeable liner is adhesively bonded to its outer surface, said liner being porous to the extent of allowing cryogenic temperature fluids in a liquid state within said vessel to permeate as a gas into said fiber-reinforced foam insulation resulting in a gaseous envelope and a gaseous-liquid interface within the insulation and a state of near equilibrium pressure across said liner, thereby containing said cryogenic fluids in a liquid state in spaced relationship to said supporting wall.

2. An internally insulated cryogenic fluid holding vessel as defined in claim 1, wherein said liner consists of fabric impregnated with organic resins and bonded to the fibers within said foam insulation, said liner having a controlled resin content of approximately percent by weight so as to result in a liner tensile strength greater than the stress developed in the restrained liner when exposed to cryogenic temperature fluid.

3. An internally insulated cryogenic fluid holding vessel as defined in claim 1, wherein a layer of porous electrically conduiting film is adhesively bonded to the surface of said liner adjacent to the cryogenic fluid to serve as a static electrical discharge element and to serve as a barrier against flame propagation eminating from accidental fires within said vessel.

4. An internally insulated cryogenic fluid vessel as defined in claim 1, wherein saidfiber-reinforced foam and liners are prefabricated in the form of long narrow interlocking segments which are capable of conforming to thecontours of the vessel when low pressure is ap' plied to achieve intimate contact between the vessel wall and the prefabricated segments during the bonding operation inside the vessel.

5. An internally insulated cryogenic fluid vessel as defined by claim 1, wherein a non-metallic tiedown is anchored to the vessel wall and extends through the insulation and liner to serve as high load attach points to support slosh baffles and other internal structures.

6. A vessel for receiving liquified gas at cryogenic temperatures as set forth in claim 1 wherein a second thickness of foam with a second permeable liner thereon is bonded in overlapping relationship to the first mentioned liner.

7. A vessel for receiving liquified gas at cryogenic temperatures as set forth in claim 6 wherein vertical corners are formed at the intersection of inner hull walls, said vertical corners comprising foam posts wrapped in a fiber glass lining, vertical edges of said foam bonded to said inner hull abutting said foam posts, and fiber glass splices applied over abuttin edges.

8. Avessel for receiving liquified gas at cryogenic I temperatures as set forth in claim 1 wherein said foam with liner bonded thereto is prefabricated in segments and is bonded together with overlapping liner strips bonded to splice adjacent liner edges together to prevent heat leakage paths between segments.

9. A vessel for receiving liquified gas at cryogenic temperatures as in claim 1 wherein said foam has X, Y and Z oriented reinforcing fibers therein, said Z fibers passing through the thickness of said foam with Z fiber ends on one side bonded to said vessel and Z fiber ends on the other of said foam being bonded to said liner.

10. An internally insulated cryogenic fluid vessel as defined in claim 9, wherein hooks are attached to the vessel wall so as to penetrate the back surface of the insulation and through the plane of said X and Y fibers to hold the insulation segments in position until the adhesive bond between the fiber-reinforced foam and the vessel wall can harden and become an effective bond.

* v a a 

1. A vessel for receiving liquified gas at cryogenic temperatures as low as -423*F., said vessel having a supporting wall to which is bonded oriented fiber-reinforced plastic foam to which a permeable liner is adhesively bonded to its outer surface, said liner being porous to the extent of allowing cryogenic temperature fluids in a liquid state within said vessel to permeate as a gas into said fiber-reinforced foam insulation resulting in a gaseous envelope and a gaseous-liquid interface within the insulation and a state of near equilibrium pressure across said liner, thereby containing said cryogenic fluids in a liquid state in spaced relationship to said supporting wall.
 2. An internally insulated cryogenic fluid holding vessel as defined in claim 1, wherein said liner consists of fabric impregnated with organic resins and bonded to the fibers within said foam insulation, said liner having a controlled resin content of approximately 60 percent by weight so as to result in a liner tensile strength greater than the stress developed in the restrained liner when exposed to cryogenic temperature fluid.
 3. An internally insulated cryogenic fluid holding vessel as defined in claim 1, wherein a layer of porous electrically conduiting film is adhesively bonded to the surface of said liner adjacent to the cryogenic fluid to serve as a static electrical discharge element and to serve as a barrier against flame propagation eminating from accidental fires within said vessel.
 4. An internally insulated cryogenic fluid vessel as defined in claim 1, wherein said fiber-reinforced foam and liners are prefabricated in the form of long narrow interlocking segments which are capable of conforming to the contours of the vessel when low pressure is applied to achieve intimate contact between the vessel wall and the prefabricated segments during the bonding operation inside the vessel.
 5. An internally insulated cryogenic fluid vessel as defined by claim 1, wherein a non-metallic tiedown is anchored to the vessel wall and extends through the insulation and liner to serve as high load attach points to support slosh baffles and other internal structures.
 6. A vessel for receiving liquified gas at cryogenic temperatures as set forth in claim 1 wherein a second thickness of foam with a second permeable liner thereon is bonded in overlapping relationship to the first mentioned liner.
 7. A vessel for receiving liquified gas at cryogenic temperatures as set forth in claim 6 wherein vertical corners are formed at the intersection of inner hull walls, said vertical corners comprising foam posts wrapped in a fiber glass lining, vertical edges of said foam bonded to said inner hull abutting said foam posts, and fiber glass splices applied over abutting edges.
 8. A vessel for receiving liquified gas at cryogenic temperatures as set forth in claim 1 wherein said foam with liner bonded thereto is prefabricated in segments and is bonded together with overlapping liner strips bonded to splice adjacent liner edges together to prevent heat leakage paths between segments.
 9. A vessel for receiving liquified gas at cryogenic temperatures as in claim 1 wherein said foam has X, Y and Z oriented reinforcing fibers therein, said Z fibers passing through the thickness of said foam with Z fiber ends on one side bonded to said vessel and Z fiber ends on the other of said foam being bonded to said liner.
 10. An internally insulated cryogenic fluid vessel as defined in claim 9, wherein hooks are attached to the vessel wall so as to penetrate the back surface of the insulation and through the plane of said X and Y fibers to hold the insulation segments in position until the adhesive bond between the fiber-reinforced foam and the vessel wall can harden and become an effective bond. 